This disclosure relates to a sensor that detects skewed or disconnected adjacent movable components, and more particularly to a sensor that detects skewed or disconnected aircraft control surfaces such as slats or flaps, for example.
Aircraft wings employ high-lift devices that are often referred to as auxiliary airfoils or control surfaces. During takeoff and landing of the aircraft, a pilot can extend these control surfaces from a leading or a trailing edge of a wing to increase aerodynamic lift. When extended, the surfaces increase the effective size, curvature, camber, and area of the wing. This extension increases the lift of the wing for slow-speed flight. Control surfaces that extend from the leading edge of the wing are referred to as slats, while control surfaces that extend from the trailing edge of the wing are referred to as flaps. Slats are used primarily to increase lift at large angles of attack, while flaps are designed primarily to increase lift during landing.
An actuation system is used to extend or retract the control surfaces. Single or multiple actuators can be used to drive a single control surface. Also, a plurality of actuators can be coordinated for a control surface. A control surface actuator is typically a geared device located in the wing that is driven by a power source, such as an electric motor for example.
When two independent actuators drive a single control surface, only limited asymmetrical movement of the leading or trailing edge, respectively, of a slat or flap that is not parallel to the leading or trailing edge of the wing, respectively, can be tolerated. Such misaligned movement is called “skew.” If one of the actuators fails, skew of the surface that the actuator drives may occur. This skew may jam a control surface mechanism, thereby restricting control of the aircraft. A surface may jam if the forces on the surface are asymmetrical. If both actuators driving the same surface fail, the surface may separate from the wing and be lost.
A single actuator can be used to actuate a control surface; however, this method does not supply the desirable redundancy that multiple actuators afford. Multiple actuators provide a margin of safety. Use of multiple actuators, however, requires synchronization, which requires additional complexity. In addition, the control surface must be structurally capable of withstanding the force of a failed single actuator while the remaining actuator or actuators apply force. Thus, it is important to be able to detect relative movement between adjacent movable control surfaces, i.e. slats or flaps.
In one known configuration, a sensor includes a reed switch and magnet that are used to sense movement between adjacent movable control surfaces. A reed switch on one arm of the sensor is held close to a magnet on another arm of the sensor by an aluminum fuse, i.e. a mechanical fuse, which forms a closed switch. When the fuse breaks due to a certain amount of movement between adjacent movable panels, a leaf spring causes the reed switch and the magnet to separate to open the switch.
One disadvantage with this traditional sensor is that it can be unreliable under certain conditions. Further, it is difficult to assemble and requires different parts to be incorporated into right hand and left hand wing positions. The reed switch may fail in the closed position, a failure mode which is not detected by the control unit. This fault may go undetected on the aircraft until maintenance personnel perform a manual check of each sensor, which typically occurs during an aircraft level periodic maintenance interval.
Accordingly, there is a need for a more reliable, cost-effective, sensor that has few parts and is easier to assemble. Further, the new design must fit the same envelope as the current design